The effect of selected essential oils on rape pathogens such as Sclerotinia sclerotiorum, Phoma lingam, Rhizoctonia solani and Fusarium oxysporum was estimated in vitro studies. S. sclerotiorum showed the lowest susceptibility to the examined essential oil treatments. The thyme oil displayed the highest fungistatic effect and suppressed the culture growth of all tested fungal species when applied at the concentration of 0.2 and 0.02%. The lemongrass oil applied at the concentration of 0.2 and 0.02% inhibited the culture growth of the examined species from 90 to 100%. The tea tree and grapefruit essential oils applied and the concentration less than 0.2% showed poor effectiveness or no fungistatic effect on F. oxysporum and S. sclerotiorum.

Tansy phacelia (Phacelia tanacetifolia Benth.) is considered a disease-resistant plant. The aim of the study was to determine which fungi (pathogens and saprofites) colonize phacelia plants. The greenhouse and field experiments were conducted in 2016. Phacelia plants were treated with fungicides from different chemical groups. Three combinations of products in the greenhouse experiment and 4 combinations in the field experiment were used. Plants without any protective treatments were used as a control. Parts of plants showing some disease symptoms were selected for isolation of saprotrophic and pathogenic fungi. The isolated and identified fungus species obtained from individual samples differed qualitatively and quantitatively. Among the pathogenic fungi the most important were Fusarium spp. [mainly Fusarium solani (Mart.) Sacc., Fusarium avenaceum (Fr.) Sacc., Fusarium equiseti (Corda) Sacc. and Fusarium oxysporum Schltdl.], Botrytis cinerea Pers., Sclerotinia sclerotiorum (Lib.) de Bary, Alternaria alternata (Fr.) Keissl. and Pythium irregulare Buisman. In some cases large differences in the occurrence of pathogens have been observed, depending on the site of the experiment (field and greenhouse) and on the type of fungicides.